Thermionic valve apparatus for use on very short wave lengths



Oct. 15, 1949.

N. E. DAViS ET AL THERMIONIC VALVE APPARATUS FOR USE ON VERY SHORT WAVELENGTHS 3 Sheets-Sheet 1 Filed Feb. 2'7, 1955 INVENTORS NORMAN a. DAVISERNEST GREEN BY ALFRED w. HALL ATTORNEY.

Oct. 15, 1940. N. E. DAViS ET AL THERMIONIC VALVE APPARATUS FO R USE ONVERY SHORT WAVE LENGTHS s Sheets-Sheet 2 Filed Feb. 27, 1935 INVENTORSNORMAN E. DAVIS ERNEST GREEN ALF o w. HALL mrw l/ ATTORNEY Oct. 15,1940. N. E. DAVIS El AL 2,218,309

THERMIONIC VALVE APPARATUS FOR USE ON VERY SHORT WAVE LENGTHS Filed Feb.27, 1935 Sheets-Sheet 3 INVENTORS. NORMAN E. DAVIS ERNEST GREEN BYALFRy. HALL ATTORNEY.

Patented Oct. 15, 1940 UNITED STTES THERMIONIC APPARATUS FOR USE ON VERYSHORT WAVE LENGTHS Norman Eustace Davis, Ernest Green, and Alfred WeedonHall, Chelmsford, England, assignors to Radio Corporation of America, acorporation of Delaware Application February 27,1935, Serial No. 8,470In Great Britain March 10, 1934 7 Claims.

This invention relates to thermionic valve apparatus for use on veryshort wave lengths and more specifically to thermionic valvearrangements suitable for use in radio circuits adapted to operate uponwave lengths of the order of ten meters or less.

The invention may be utilized to provide an improved very high frequencyamplifier and there will later be described in this specification apreferred form of very high frequency amplifier which can besatisfactorily employed on a wave length of about six to eight meters.

As is well known, satisfactory and efiicient thermionic amplifiers, foruse on very short wave lengths of the order in question and foroperation at high power, are dificult to construct. The requirements ofsuch a high power very short wave amplifier may be generalized asfollows:

(a) The circuit must be electrically symmetrical.

(b) There shall be electrical symmetry relative to earth. a

(c) Stray and uncontrollable capacitative and electromagneticcouplingsshall be avoided. (d) Interconnecting leads shall be as shortas possible and as few as possible.'

(e) The whole'assembly shall be compact and rigid.

The present invention provides a thermionic valve apparatus in which theabove requirements are satisfied to a very high degree, said apparatusbeing moreover comparatively cheap and easy to construct.

As will be seen more clearly later, the principal features of theinvention reside in (1) the arrangement of symmetrically connectedthermionic valves in containing screens or housings which also serve aselectrodes in anode tuning and neutralizing condensers; (2) theprovision of input and output circuits each symmetrically formed andeach constructed as an easily re-- movable unit so that it may beadjusted when away from the other apparatus; (3) the provision ofvariable input and output couplings which 5 may be varied by moving theinput and output circuits as units without at all upsetting the symmetryand electrical constants of the whole arrangement; (4) the utilizationas part of the output inductance of an arrangement of metal tubes whichare also employed to carry cooling water to the valves and the provisionin association with-said metal tubes of tuning means whereby the outputinductance may be varied without interfering with the water connectionsand with a minimum of alteration to subsidiary apparatus; (5) theutilization as part of the output inductance of the arrangement of tubeswhich also serve to conduct cooling water to and from the valves, andthe construction of said tubesin such "manner that'they present adesired, relatively high resistance and thereby give the whole amplifiera, desired wide, band-pass characteristic. This last feature is onewhich is only required in cases where the amplifier is intendedtoamplify a carrier wave modulated with 10 a wide band of frequencies, e.g., a television modulated carrier wave, and in cases where the wideband pass characteristic isnot required,

the tubes would be constructed to be of low high-frequency resistance. I1.3

The invention is illustrated .in'the accompanying drawings'which' relateto a pre'ferred form of high frequency amplifier suitable for use on awave length of the order of from 6 to 8 meters.

In the drawings: 20 Fig. lisacircuit diagram; Fig. 2 is aside elevationshowing the amplifier general arrangement as seen through the side wallof its container cubicle;

Fig. 3 is a front'elevation of the'arrangement 5 shown in Fig. 2, theparts being again shown dotted since they are behind the front panel ofthe cubicle;

Fig. 4 is a plan view of Fig. 2 rotated showing the principal parts ofthe apparatus on 30 the output side of the screen V;

Fig. 5 'is a sectional elevation on a reduced scale through the line Q,Q of. Fig. 4, again showing only the principal parts; and

Fig. 6 is an end view of the apparatus shown. 35 in Fig. 5. Likereferences have been used for like parts throughout the figures.

Referring to 'Fig. 1, tnehigh frequency input, I e. g., modulated highfrequency, is fed through adjustable condensers 2%, 25 to a coil 280.which 40 is variably coupled to a coil 18 tuned bya shunt condenser l9.Opposite ends of the tuned circuit l8, it are connectedthroughfcondensers l5, id as shown, to the grids of two symmetricallyarranged valves or electronictubes l and 2 which 4 are of the knownsingle ended typehaving watercooied anodes IA and 2A which form parts ofthe envelopes. The vaives are cross neutralized by condensers 8Xconnected between theanode of each valve and the grid of the other. Theanode are. connected together through an inductance 9a and b, which isshunted by a .variable tuning condenser arrangement 5YY andthe-inductance 9a and 9b is variablycoupled to a coil i la whose endsare connected through adjustable condensers 55 mounted, with its anodelo or 2a downwards, in

a triangular metal chair 3 or 4, each chair having. two vertical walls Xand Y which are arranged so as to substantially shield the supportinginsulators W (see particularly Fig. 6).. The walls X of the chairs areinclined towards one another and extend well beyond the walls Y, asshownin Fig. 4. The walls X are in electrostatic relationship with conductiveplates 8.,(seeFig. 1)

which, with the said walls X constitute the cross connected neutralizingcondensers 8X of, Fig.1. The chairs as a whole are, of course; in directelectrical L contact; with the; anodei jacketsyof the valves which areof course, at'anode potential.

Theplates 8-. are, movable, beinghingedupon hinges clearly shownin;Figj. 4 and, as will be at once apparent, are convenientlyarrangedfor accurate adjustment and. neutralization: The plates 8' arecross, connectedto' the grids of the valve throughv conductors L3 andltrespectively; thus the conductor, 43 connects oneof the plates 8through a condenser I6 tothe-gridof the valve at l in Fig. 4, whilethe;other plate 8 is connectedthrough conductor"I4.- and condenser [E tothe grid; ofthe valve at 2. The; grid leads from the condensers 15,15are shown broken ofi in Fig. 4, but they continue in a direction tobisect the angles at -the corners ofthetriangular chairs, The ends ofthe conductors I'3 and l4 remote from the platesufi, arealso.electrically and mechanically unitedwith conductors- Ila which passthrough apertures in a screen-wall V and are formed at their end-5,815;Clamps or sockets for rectivin or. clamping plugs :formed on or ryin therid tunin coil l-8;'; s ;is l rl shown in Fig. 3. It will. beg seenthat:this constructionresults in .avery. rigid'assemblyhwith very shortcross, ancb interconnecting leads .and

good; shielding of. thejinput, circuit. The coil I8 is tuned byacondenser l 9 (see Fig. 3);;theplates of which; are .ca-rried'gupon;stems mountedupon the same iIiSlllHzlEOlSgthfit. help tocarry. the'structures l1, Ila, l3, l,4-,'l'5 -,and.l.6.- .Fur,-thermore; as

will. appearmore clearly later, the inductance is is; at right.:anglesfltogthe inductance. in; the output circuit; The; anodes, ofv thevalves are cooled by waterledthereto;throughpipes 9a, 9b

' which also; constitute the; anode. inductances.

- ment will behest seen from Figs. 4, 5 and 6.

These pipes are in parallel, and their'arrange- Water connections aremade to these pipes via pipes in, la and anode potential is applied viathe points at which pipes Iii, lfiajoinpipes 9a and 9b respectively. Theanode inductance is tuned bythe condenser constituted by the arrangementshown at 5 in electrostatic cooperation with the plates Y of thetriangular chairs. The arrangement at-5 consists of a hollow open endedcopper box formed of two halves which may be adjusted with regard totheir respective distances from the plates Y (see Fig. 4), the whole boxbeing mounted as shown in Fig. 5, so that it may be slid longitudinallywith respect to the chairs. Th-eguide plates along which sliding motionoccurs are shown at B; and I is an attachment for a suitablemechanicaldrive. In effect, the box 5. iorms a ,plate'. whose distance 'of' a coilHa which is positioned between and coupled to coils formed in the pipes9a, 9b, the

. ends of the coil I la being connected each to one terminal'of; anadjustable condenser llb or No,

the remaining terminal of one of the two condensers H2), H beingdirectly earthed to frame and the remaining terminal of the other ofthese two condensers being connected to a tubular output feeder shown atcl (Fig. 4). The whole unit Ha, Hb, He may, as will be obvious fromFigs.

.4 and 5, easily be withdrawn and when withdrawn after detaching pipesIlla, adjusted and balanced-accurately. When the unit-isin positioninthe apparatus,-. the couplingbetween. Ila. and-the inductances:constituted by the circular bends in thepipes 9a. and 9b may, bevariedwithout at all disturbing the, symmetry or, electrical contents ofthe arrangement, by sliding thewhole output unit consisting ofthe partsHa, II b, Hc along guides shown .at l2, [2a in-Fig..4.- I Theinputcircuit whichis very similar is againmade up of; a} unitconsistingofacoil 20a, condensers 2011 and. 200, and, as before,v the:coupling/can. be varied by vertically sliding the whole. unit 20a, 20b,200 along guides 24 (seeFig. 3) this adjustment being. again. one thatcan be made. without disturbing the symmetry ,or. electrical constants.

The inputfeeder is, shown. at. 22in. Fig. 2. In Figs. 2 and 3, 23representsftheglass. portions of the envelopes of the. valves; whose.anode. jackets are in the chairs-3 and 4 (the grid :lead-passing outthrough one of these glass portions to the condenser I6 is clearly shownin- Fig. 2.) 1 and 24 and 25 are filament bus bars.

. It will be noticed that, the-extensions of the walls ,X of thechairsbeyond. the triangular apices assists in electrically isolatingthe arms I3; and M of the bridge circuit. Thewalls X.-Y substantiallyshield the insulators w and thus minimize dielectric losses byadvantageously distributing; the high frequency fields. Further, themaintuning control,;whichv islthe device for liding;;the:- copper box.S-andWhich enables. the tuning; ofthe whole 'circuit. when on. power, isat earth potential while the condenser arrangement Y-Y is extremelyrigid andshouldbe ofi highly constant capacity. Again, theinsulatorsupporting: this condenser is'in: the electrical center. of

- the anode-circuit, andt-herefor there wouldbe noj heating ordielectric; losses.at..this point... If: inany particularinstallationan. anode-2m.- ductance; whichis lower. t-han.that which canbe obtained-from an arrangement as so 'fardescribed andillustrated isrequired thi s may be effected by dispensing with-the circular bendsin-the tubes Bag and; 912; A. preferred-arrangement,. however, which;may be usedr-whether such circular bends are-present or not, and .whichhas the advantage of permitting; easy; adjustmentof inductance, is that;illustrated in. Fig. .4. (the corresponding parts; are,-- not shown inFig, 5'. for.- the-sake-of clarity.) and consists: of..t woadditional.metal tubes U of appropriate. diameter, v surrounding thertubes 9a; andSbg-theysaid-tubes U being connected through a'thirdtubular member T oflthe same. or.- substantially; thesame diameter. .The structure.- 'I UU.isslidably arrangedlongitudinally and by sliding this structure alongthe pipes, the

anode inductance may be accurately adjusted as required withoutinterfering with thewater supply to the valves. It will be. appreciatedthat the provision of the member T, though convenient practically, is byno means essential, for in many cases the, required inductance .could beobtained by using tubes U of fixed length surrounding the tubes, 9a and9b andrigidly connected thereto, there being no bridge piece.

Apparatus as illustrated in the accompanying Figs. 2 to 6 may, withslight modification, be very satisfactorily employed for theamplification' and transmission of a very high, frequency carrier wave,e. g., of six to eight meters, modulated with a very wide band ofmodulation frequencies, e.- g., for television purposes. For example, avery slight modification is required in order that the illustratedapparatus may be satisfactorily employed, not as a final outputamplifier, but as an intermediate modulated amplifier having a very widefrequency band pass, as for television signals. The modificationconsists merely in so arranging matters that the anode inductancepresents substantial resistance whereby the inductance/resistance ratiois made of the required value to give the required wide band pass.

A preferred method of obtaining the necssary resistance consists inspraying the copper tubes 9a, 9b with soft malleable annealed iron orother material having similar electrical properties. If this be done,the high frequency currents, which will pass by reason of skin effectmostly along the outsides of the conductors 9a, 91), will sufferconsiderable loss due to the high permeability of the iron surface,while at the same time the advantages of copper piping for carrying thewater are still obtained. In broad principle, this method of obtainingloss to secure a desired inductance/resistance ratio consists inutilizing the water passing down the tubes 9a, 9b to dissipate therequired proportion of energy; that is to say, the high frequency lossis induced by reason of the external soft iron coating, but the heatgenerated by that loss is quickly and efficiently dissipated by reasonof heat conduction through the copper pipe to the water. It is foundthat it is possible to make the anode circuit loss one third of thetotal output by the method described, and thus to secure a wide bandpass characteristic. The advantages of the method described will be atonce apparent when said method is compared with the usual known methodof obtaining a desired relatively low inductance/resistance rationamely, the known method which consists in loading back a suitableresistance component from the load. dif the load were, as is: usuallythe case, a grid circuit and this known method were employed, then,since a relatively small amount of power is; required for full gridexcitation, a non-inductive load would have to. be built around the gridcircuit in order to take the additional load required to throw-back tothe anode circuit the required resistance and loss. For frequencies ofthe order in question, the provision of such a load circuit will usuallybe most undesirable, and in fact the stray capacity of such a loadcircuit would be likely to prejudice the tuning of the grid circuit atthe very high frequencies concerned.

Although, in the specifically described and illustrated embodiment ofthe invention, triodes are employed, the said invention is not limitedto the use of this type of valve, and screen grid yvalvesgfor example,could be used with advantage. ,Verylittle alteration would be required--to adapt the illustrated arrangement to incorporate screen gridvalves, and if such Valves were currentblocking condensers. Even ifscreen grid valves were employed for power amplifier work, it isprobable that balancing condenser 8X would still be necessary, or at anyrate desirable.

What is claimed is: 1. A vacuum tube amplifier systemhaving a 1 pair ofmutuallycoupled input coils and a. pair of mutually coupled outputcoils, each pair of said input and output coils being arranged at rightangles to each other pair, an input circuit comprising one of said inputcoils having a condenser in series with each side of said input coil andterminals on said input circuit, means for sliding said last mentionedinput coil and condensers as a unit into operative relation with theother input coil for said vacuum tube amplifier, an output circuitconsisting of one of said output coils having a condenser in series witheach side of said output coil and. terminals on said output circuit, andmeans, for sliding said last mentioned coil and condensers as a unitinto operative engagement with the other output coil for coupling withsaid vacuum tube amplifier.

2. Apparatus as claimed in the preceding claim, characterized by thefact that said Vacuum tube amplifier includes a pair of tubes connectedin push-pull fashion.

3. In combination, two pairs of metallic coridenser plates mounted andarranged opposite each other, each plate of said pair being located atan acute angle with respect to each other, an electronic tube supportedwithin each pair of said plates whereby the anode of said tube isconnected to said plates and acts as part of the anode tuning condenserfor said tube, and means cooperating with the other of said angularlyarranged plates whereby said other plate serves as part of theneutralizing condenser for the grid of an oppositely arranged tube.

4. In combination, two pairs of triangular metallic condenser platesarranged opposite each other, an electron tube mounted within and havingits anode connected to each pair of triangular plates, means including aplurality of adjustable plates interposed between each pair oftriangular plates for tuning the anode circuit of said tubes, and meansincluding two other adjustable plates in capacitive relation with eachpair of triangular plates for neutralizing the inter-electrode capacityof an oppositely arranged tube.

5. Apparatus as claimed in the preceding claim, characterized by thefact that coils are constructed of hollow tubular material to permit theflow of a cooling fluid therethrough, said coils having their axes atright angles to each other and connected across the plates and grids ofsaid tubes.

6. In combination, two pairs of triangular metallic condenser platesarranged opposite each other, an electron tube mounted within and havingits anode connected to each pair of triangular plates, means including aplurality of adjustable plates interposed between each pair oftriangular plates for tuning the anode circuit of said tubes, meansincluding two other adjustable plates in capacitive relation with eachpair of triangular plates for neutralizing the interelectrode capacityof an oppositely arranged tube, a hollow tubular conductor connectedacross the anodes of said tubes, and a, plurality of metallic sleevesmounted about portions of said hollow conductor for varying theinductance thereof.

7. An amplifier system comprising two electron amplifier tubes, a pairof mutually coupled inductance input coils and a pair of mutuallycoupled output coils, each pair of input and output coils being arrangedat right angles to each other pair, an input circuit comprising one ofsaid input coils having a condenser in series with each side of saidinput coil and terminals on said input circuit, means for sliding saidlast mentioned input coil and condenser as a unit into operativerelation with the other input coil of said electron amplifier tube, twopairs of triangular metallic condenser plates arranged opposite eachother, each one of said electron tubes mounted within and having itsanode connected to each pair of triangular plates, means including aplurality of adjustable plates interposed between each triangular platefor tuning the anode circuit of said tubes, and means including twoother adjustable plates in capacitive relationship with each pair oftriangular plates for neutralizing the inter-electrode capacity of anoppositely arranged tube, an output circuit consisting of one of saidoutput coils and having a condenser in series with each side of saidoutput coil and terminals on said output circuit, and means for slidingsaid last mentioned coils and condensers as a unit into operativeengagement with the other output coil for coupling with said amplifier.

NORMAN EUS'I'ACE DAVIS.

ERNEST GREEN. ALFRED WEEDON HALL.

